1. Field of the Invention
The present invention relates to a piezooscillator having a piezoelectric resonator.
2. Description of the Related Art
As an example crystal oscillator having a crystal resonator being a piezoelectric resonator, that having a structure shown in FIGS. 7A, 7B, 7C, 7D is known. In FIG. 7, “11” denotes a crystal resonator having a structure in which a crystal piece and a pair of excitation electrodes are enclosed in a square package while being held, for example, by a support member. In the drawing, “12” denotes a base substrate mounting the crystal resonator 11 thereon, and an oscillation circuit to oscillate the crystal resonator 11 is built in the base substrate 12. In the drawing, “13” denotes a lead wire, and, for example, one end of the lead wire 13 is connected to each excitation electrode in the package of the crystal resonator 11. Further, the other end of the lead wire 13 is connected to an electrode 14 provided on the base substrate 12, and the crystal resonator 11 and the electrode 14 provided on the base substrate 12 are electrically connected via the lead wire 13. In the drawing, “15” denotes a cover provided on the base substrate 12 so as to cover the crystal resonator 11, and it is designed that, when the crystal resonator 11 oscillates, for example, this crystal oscillator being denoted by “1A” is heated from outside the crystal oscillator 1A by a heating means such as a heater so that a space 16 surrounded by the cover 15 and the base substrate 12 is kept at a constant temperature. Specifically, this crystal oscillator 1A is structured as an OCXO (Oven Controlled Crystal Oscillator). Note that “17” in the drawing denotes an electrode provided on a reverse face of the base substrate 12.
Further, the description will be given of the other example crystal oscillator with reference to FIGS. 8A, 8B, 8C, and “18” in the drawing denotes an oscillation circuit board having a built-in oscillation circuit to oscillate the crystal resonator 11. In the drawing, “10” denotes a base substrate, and the oscillation circuit board 18 is fixed to the base substrate 10 in a floating state therefrom via support posts 19 being hard lead pins. Note that, although the drawing is omitted here to avoid complication, the support posts 19 are connected the electrods provided on the base substrate 10 and the oscillation circuit board 18 respectively via a solder or the like, so that the electrode provided on the base substrate 10 and the electrode provided on the oscillation circuit board 18 are electrically connected. Except such a difference, this crystal oscillator being denoted by “1B” is structured in the same manner as in the previously-described crystal oscillator 1A in FIG. 7, and in the crystal oscillator 1B, the crystal resonator 11 does not contact the base substrate 10 directly, in which the heat of the crystal resonator 11 heated when the crystal resonator 11 oscillates as described above is prevented from leaving to the base substrate 10 and diffusing outside the crystal oscillator 1B, suppressing the consumption power to keep the space 16 at the constant temperature, as a result thereof.
Meanwhile, the crystal oscillator is used in electronic equipment such as mobile communication equipment and transmission communication equipment or in a base station as a high-precision reference oscillation source, however, when transporting the crystal oscillator, or when installing the crystal oscillator into the electronic equipment or the base station, there is a threat for the crystal oscillator of suffering a shock applied from outside and, for example, when the crystal oscillator in FIG. 7 suffers the shock, the shock is conveyed from the base substrate 12 directly to the crystal resonator 11 and, at the same time, the shock is conveyed from the base substrate 12 to the crystal resonator 11 via the lead wire 13. In addition, when the crystal oscillator in FIG. 8 suffers the shock from outside, the shock is conveyed via the base substrate 10, the support post 19 and the oscillation circuit board 18 sequentially to the crystal resonator 11, in which the crystal resonator 11 also has a threat of suffering a shock of the same level as of the shock applied from outside.
On the back of downsizing of the crystal resonator in which the package and the crystal piece are coining close to each other, when a shock is applied from outside directly to the crystal resonator 11, an oscillation stop is possibly caused, for example, by tie crystal piece contacting the package. Further, even though a positional difference of the crystal piece is small, when a high-precise frequency is required to be set, a frequency difference not meeting the specification is possibly caused. The shock-resistance of the crystal resonator is affected by the size, shape and thickness of the crystal piece and the shape of a support member supporting the crystal piece, therefore, the shock-resistance is conventionally improved by contriving the structure of the crystal resonator, however, the structure is made complicated due to the easily-broken crystal piece and the downsizing of the crystal resonator, so that a man-hour is increased and productivity is degraded, and further the downsizing is caused to be prevented. Accordingly, under these circumstances, a downsized crystal oscillator with higher shock-resistance has been demanded.